This invention is generally directed to processes for the preparation of bisphenols such as gem-bis(hydroxyalkyl)alkanes, and more specifically to processes for preparing 1,1-bis(p-hydroxyphenyl)cyclohexane, commonly referred to as bisphenol (Z). Thus, in accordance with the process of the present invention there can be prepared certain bisphenols, inclusive of bisphenol (Z) by the reaction of a ketone, a hydroxyarene such as a phenol, and an alkylhalosilane, which functions as a condensation mediating component. There is thus enabled with the process of the present invention a simple economical method for the synthesis in high yields of bisphenols, which can be selected as a monomer for the preparation of polycarbonates that are useful as binders for charge transport molecules, and photogenerating pigments incorporated, for example, into layered photoconductive imaging members, reference U.S. Pat. No. 4,265,990, the disclosure of which is totally incorporated herein by reference. In one important embodiment of the present invention, there is provided a process for the preparation of specific bisphenols by the reaction of a ketone, a phenol and an alkylhalosilane mediating agent in the presence of a catalyst, wherein there results products in yields of, for example, greater than 65 percent, which products are substantially free of undesirable impurities. The aforementioned bisphenols, particularly bisphenol (Z) as indicated herein, can be selected for the preparation of polycarbonate resins, which resins can be utilized as binder components in layered imaging members. More specifically, the polycarbonates obtained can be selected as resinous binders for arylamines, inclusive of triarylamine charge transport components.
Processes for the preparation of bisphenols are known, and generally involve the condensation of two mole equivalents of phenol with one mole equivalent of carbonyl compound in the presence of an acid catalyst. Acid catalysts employed for the aforementioned condensation are concentrated hydrochloric acid, gaseous hydrogen chloride, concentrated sulfuric acid, hydrogen fluoride, hydrogen bromide, boron trifluoride, boric acid, ferric chloride, phosphorus chloride, phosphorus pentoxide, benzenesulfonic acid, and the like. Although these acid catalysts, in particular gaseous hydrogen chloride, are very effective in promoting the condensation of phenols with sterically accessible ketones such as acetone, they are not effective for the preparation of bisphenols, especially bisphenol (Z) derived from the sterically demanding small cyclic ketone such as cyclopentanone or cyclohexanone. The condensation with small ring ketones does not normally proceed in a rapid manner, and the yield of product is generally less than desirable. The aforementioned reaction, especially when accomplished in the presence of hydrogen chloride as a catalyst, is illustrated in U.S. Pat. No. 4,304,899. Similar teachings are presented in U.S. Pat. Nos. 1,760,758; 2,069,560 and 2,069,573, wherein there are disclosed methods for the preparation of bisphenols with hydrogen chloride catalysts.
In U.S. Pat. No. 2,858,342, there is disclosed, for example, a method for the preparation of bisphenols utilizing alkali metal phenoxides, or alkaline earth metal phenoxides of the phenol being reacted; and wherein cyclohexanone may be selected as a reactant. There resulted in one process embodiment illustrated in this patent, reference Example XI, the preparation of 1,1-bis-(4-hydroxyphenyl)cyclohexane. Also, there is described in U.S. Pat. No. 4,423,352 a process for the preparation of bisphenols utilizing a cation exchange resin modified with a pyridine alkanethiol as a catalyst.
Moreover, U.S. Pat. No. 1,977,627 describes a process for the preparation of bisphenols wherein 65 to 75 percent sulfuric acid is selected as the catalyst. With the process as disclosed in the '627 patent, there is avoided a complex apparatus, and moreover corrosion problems are substantially reduced. In comparison to the processes mentioned herein, wherein, for example, hydrogen chloride is selected as a catalyst, the process of the '627 patent proceeds in a less rapid manner and the product resulting is more difficult to purify. Additionally, it is known that certain sulfur compounds such as sulfur dichloride, sodium thiosulfate, sodium sulfide and the like can be selected for the synthesis of bisphenols, reference for example U.S. Pat. No. 2,923,744, which illustrates a process for the preparation of bisphenols wherein there is selected mercaptoalkanesulfonic acids in catalytic amounts for the purpose of promoting the condensation of phenols and carbonyl compounds. Similarly, selenium and tellurium compounds are effective catalysts for bisphenol synthesis, reference for example U.S. Pat. No. 2,762,846.
Accordingly, while processes for the preparation of bisphenols are known, there is a need for new processes particularly those wherein products with acceptable yields are obtained. More specifically, there is a need for processes for the preparation of bisphenols that are economical, and where there are provided excellent yields of the product desired. There is also a need for efficient, simple processes for the preparation of bisphenols. Additionally, there is a need for processes for the synthesis of bisphenols wherein the products resulting are substantially free of impurities, enabling their use, for example, in the preparation of polycarbonates that can be selected as binders in electrophotographic imaging members. In addition, there is a need for economical processes that enable the preparation of bisphenols where the reaction can be rapidly accomplished at a relatively low temperature. Another need resides in the provision of a simple efficient process wherein the bisphenol product resulting can be easily purified such as by simple recrystallization, and the excess of reagent selected can be recovered by filtration. Also, there is a need for efficient processes that permit the preparation of certain bisphenols wherein troublesome gaseous catalysts are avoided.